Systems and methods for diplexer circuits with leakage cancellation

ABSTRACT

Systems and methods for diplexer circuits with leakage cancellation are provided. In one aspect, a diplexer circuit including first and second radio frequency transceiver terminals and a first antenna terminal, and first and second parallel communication paths extending between the first radio frequency transceiver terminal and the first antenna terminal, and third and fourth parallel communication paths extending between the second radio frequency transceiver terminal and the first antenna terminal. The circuit also includes a first phase shifter configured to apply a first phase shift to a first radio frequency transmit signal on the first communication path, a second phase shifter configured to apply a second phase shift to a second radio frequency on the second communication path, and a third phase shifter configured to apply a third phase shift to the first radio frequency transmit signal on the third communication path.

CROSS-REFERENCE TO RELATED APPLICATION(S)

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND Field

Aspects of this disclosure relate to radio frequency (RF) communicationsystems, and in particular, cancelling signal leakage in such systems.

Description of the Related Technology

RF communication systems typically include an RF front end which couplestransmit and receive paths between a baseband processor and one or moreantennas. Such RF front ends may include power amplifier(s), low noiseamplifier(s), and/or filter(s) to process RF signals transmitted to andreceived from the antennas. One design considerations for RF front endsis to limit or otherwise reduce the amount of a transmit signal that isleaked onto a receive path.

SUMMARY

The systems, methods and devices of this disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein.

In one aspect, there is provided a diplexer circuit comprising: firstand second radio frequency transceiver terminals and a first antennaterminal; first and second parallel communication paths extendingbetween the first radio frequency transceiver terminal and the firstantenna terminal, and third and fourth parallel communication pathsextending between the second radio frequency transceiver terminal andthe first antenna terminal; a first phase shifter configured to apply afirst phase shift to a first radio frequency transmit signal between thefirst radio frequency transceiver terminal and a first diplexer on thefirst communication path, a second phase shifter configured to apply asecond phase shift to a second radio frequency transmit signal betweenthe first antenna terminal and a second diplexer on the secondcommunication path, and a third phase shifter configured to apply athird phase shift to the first radio frequency transmit signal betweenthe first diplexer and the second radio frequency transceiver terminalon the third communication path.

The second phase shifter can be further configured to coherently sum thefirst and second radio frequency transmit signals, and wherein thesecond phase shifter is further configured to coherently sum third andfourth radio frequency transmit signals received from the second radiofrequency transceiver terminal.

The first phase shifter can be further configured to destructivelycancel leakage of third and fourth radio frequency transmit signalsreceived from the second radio frequency transceiver terminal, andwherein the third phase shifter is further configured to destructivelycancel leakage of the first and second radio frequency transmit signalsreceived from the first radio frequency transceiver terminal.

The first phase shifter can include a first hybrid transmit splitter,the second phase shifter can include a second hybrid receive splitter,and the third phase shifter can include a third hybrid antenna splitter.

The diplexer circuit can further comprise: a third radio frequencytransceiver terminal coupled to the first phase shifter; a fourth radiofrequency transceiver terminal coupled to the third phase shifter; asecond antenna terminal coupled to the second phase shifter; fifth andsixth parallel communication paths extending between the third radiofrequency transceiver terminal and the second antenna terminal; andseventh and eighth parallel communication paths extending between thefourth radio frequency transceiver terminal and the second antennaterminal.

The first phase shifter can be further configured to apply a fourthphase shift to a third radio frequency transmit signal between the thirdradio frequency terminal and the first diplexer on the fifthcommunication path, wherein the second phase shifter is furtherconfigured to apply a fifth phase shift to a fourth radio frequencytransmit signal between the third antenna terminal and the seconddiplexer on the sixth communication path, and the third phase shifter isfurther configured to apply a sixth phase shift to the third radiofrequency transmit signal between the first diplexer and the secondradio frequency transceiver on the seventh communication path.

The first radio frequency transceiver terminal can be configured tocommunicate via a cellular signal, and the second radio frequencytransceiver terminal can be configured to communicate via a Wi-Fisignal.

The first phase shifter and the third phase shifter can be configured toprovide a phase shift of about 180° to the first radio frequencytransmit signal.

The first phase shifter and the second phase shifter can be configuredto provide a phase shift of about 90° to each of the first and secondradio frequency transmit signals.

The third phase shifter can be configured to apply a fourth phase shiftto a second radio frequency transmit signal between the second radiofrequency terminal and the first diplexer on the third communicationpath, and the second phase shifter can be configured to apply a fifthphase shift to a fourth radio frequency transmit signal between thefirst antenna terminal and the first diplexer on the fourthcommunication path.

The second phase shifter and the third phase shifter can be configuredto provide a phase shift of about 90° to each of the third and fourthradio frequency transmit signals.

In another aspect, there is provided a method of diplexing radiofrequency signals, the method comprising: outputting first and secondradio frequency transmit signals onto respective first and secondparallel communication paths extending between a first radio frequencytransceiver terminal and an antenna; applying a first phase shift to thefirst radio frequency transmit signal between the first radio frequencyterminal and a first diplexer on the first communication path;outputting third and fourth radio frequency transmit signals ontorespective third and fourth parallel communication paths extendingbetween a second radio frequency transceiver and the antenna; applying asecond phase shift to the second radio frequency transmit signal betweenthe antenna and a second diplexer on the second communication path; andapplying a third phase shift to the third radio frequency receive signalbetween the first diplexer and the second radio frequency transceiver onthe third communication path.

The method can further comprise: combining the first and second radiofrequency transmit signals at a splitter; and providing the combinedfirst and second radio frequency transmit signals to the antenna.

The method can further comprising: combining third and fourth radiofrequency transmit signals received from the second radio frequencytransceiver terminal at the splitter; and providing the combined thirdand fourth radio frequency transmit signals to the antenna.

The method can further comprise: destructively cancelling the first andsecond radio frequency transmit signals at a splitter coupled to thesecond radio frequency transceiver terminal.

The method can further comprising: destructively cancelling leakage ofthird and fourth radio frequency transmit signals received from thesecond radio frequency transceiver terminal at a first splitter coupledto the first radio frequency transceiver terminal; and destructivelycancelling leakage of the first and second radio frequency transmitsignals at a second splitter coupled to the second radio frequencytransceiver terminal.

In yet another aspect, there is provided a radio frequency systemcomprising: first and second radio frequency transceivers; a firstantenna; and a diplexer circuit includes first and second parallelcommunication paths extending between the first radio frequencytransceiver and the first antenna, third and fourth parallelcommunication paths extending between the second radio frequencytransceiver and the first antenna, a first phase shifter configured toapply a first phase shift to a first radio frequency transmit signalbetween the first radio frequency transceiver and a first diplexer onthe first communication path, a second phase shifter configured to applya second phase shift to a second radio frequency transmit signal betweenthe first antenna and a second diplexer on the second communicationpath, and a third phase shifter configured to apply a third phase shiftto the first radio frequency transmit signal between the first diplexerand the second radio frequency transceiver on the third communicationpath.

The second phase shifter can be further configured to coherently sum thefirst and second radio frequency transmit signals, and the second phaseshifter can be further configured to coherently sum third and fourthradio frequency transmit signals received from the second radiofrequency transceiver.

The first phase shifter can be further configured to destructivelycancel leakage of third and fourth radio frequency transmit signalsreceived from the second radio frequency transceiver, and the thirdphase shifter can be further configured to destructively cancel leakageof the first and second radio frequency transmit signals received fromthe first radio frequency transceiver.

The first phase shifter can include a first hybrid transmit splitter,the second phase shifter can include a second hybrid receive splitter,and the third phase shifter can include a third hybrid antenna splitter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one example of a communication network.

FIG. 2 is a schematic diagram of one embodiment of a mobile device.

FIG. 3 is a schematic diagram of a power amplifier system according toone embodiment.

FIG. 4 is an example embodiment of a duplexer circuit that can be usedin an FDD or TDD radio front-end.

FIG. 5 is an example embodiment of a duplexer circuit that can be usedin an FDD or TDD radio front-end in accordance with aspects of thisdisclosure.

FIG. 6 illustrates an embodiment of a splitter which can be used inaccordance with aspects of this disclosure.

FIG. 7 is another example embodiment of a duplexer circuit that can beused in an FDD or TDD radio front-end in accordance with aspects of thisdisclosure.

FIG. 8 is a flowchart that provides a method for improved RF leakagecancellation for a duplexer circuit used in a radio front-end inaccordance with aspects of this disclosure.

FIG. 9 is an example embodiment of a duplexer circuit that can be usedin an FDD or TDD radio front-end.

FIG. 10 is an example embodiment of a duplexer circuit that can be usedin an FDD or TDD radio front-end in accordance with aspects of thisdisclosure.

FIGS. 11A and 11B provide example embodiments of circuit configurationswhich can be used to connect the receive port to the duplexer circuit ofFIG. 10 in accordance with aspects of this disclosure.

FIG. 12 is another example embodiment of a duplexer circuit that can beused in an FDD or TDD radio front-end in accordance with aspects of thisdisclosure.

FIGS. 13A and 13B illustrate yet another example embodiment of aduplexer circuit that can be used in an FDD or TDD radio front-end inaccordance with aspects of this disclosure.

FIG. 14 is an example embodiment of a diplexer circuit that can be usedto couple two different communication technologies to an antenna inaccordance with aspects of this disclosure.

FIG. 15 is another example embodiment of a diplexer circuit 400 that canbe used to couple two different communication technologies to twoantennas in accordance with aspects of this disclosure.

FIG. 16 is a flowchart that provides a method for improved RF leakagecancellation for a duplexer circuit used in a radio front-end inaccordance with aspects of this disclosure.

FIG. 17 is a flowchart that provides a method for improved RF leakagecancellation for a diplexer circuit in accordance with aspects of thisdisclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

Overview of 5G Systems

The International Telecommunication Union (ITU) is a specialized agencyof the United Nations (UN) responsible for global issues concerninginformation and communication technologies, including the shared globaluse of radio spectrum.

The 3rd Generation Partnership Project (3GPP) is a collaboration betweengroups of telecommunications standard bodies across the world, such asthe Association of Radio Industries and Businesses (ARIB), theTelecommunications Technology Committee (TTC), the China CommunicationsStandards Association (CCSA), the Alliance for TelecommunicationsIndustry Solutions (ATIS), the Telecommunications Technology Association(TTA), the European Telecommunications Standards Institute (ETSI), andthe Telecommunications Standards Development Society, India (TSDSI).

Working within the scope of the ITU, 3GPP develops and maintainstechnical specifications for a variety of mobile communicationtechnologies, including, for example, second generation (2G) technology(for instance, Global System for Mobile Communications (GSM) andEnhanced Data Rates for GSM Evolution (EDGE)), third generation (3G)technology (for instance, Universal Mobile Telecommunications System(UMTS) and High Speed Packet Access (HSPA)), and fourth generation (4G)technology (for instance, Long Term Evolution (LTE) and LTE-Advanced).

The technical specifications controlled by 3GPP can be expanded andrevised by specification releases, which can span multiple years andspecify a breadth of new features and evolutions.

In one example, 3GPP introduced carrier aggregation (CA) for LTE inRelease 10. Although initially introduced with two downlink carriers,3GPP expanded carrier aggregation in Release 14 to include up to fivedownlink carriers and up to three uplink carriers. Other examples of newfeatures and evolutions provided by 3GPP releases include, but are notlimited to, License Assisted Access (LAA), enhanced LAA (eLAA),Narrowband Internet of things (NB-IOT), Vehicle-to-Everything (V2X), andHigh Power User Equipment (HPUE).

3GPP introduced Phase 1 of fifth generation (5G) technology in Release15, and plans to introduce Phase 2 of 5G technology in Release 16(targeted for 2019). Subsequent 3GPP releases will further evolve andexpand 5G technology. 5G technology is also referred to herein as 5G NewRadio (NR).

5G NR supports or plans to support a variety of features, such ascommunications over millimeter wave spectrum, beamforming capability,high spectral efficiency waveforms, low latency communications, multipleradio numerology, and/or non-orthogonal multiple access (NOMA). Althoughsuch radio frequency (RF) functionalities offer flexibility to networksand enhance user data rates, supporting such features can pose a numberof technical challenges.

The teachings herein are applicable to a wide variety of communicationsystems, including, but not limited to, communication systems usingadvanced cellular technologies, such as LTE-Advanced, LTE-Advanced Pro,and/or 5G NR.

FIG. 1 is a schematic diagram of one example of a communication network10. The communication network 10 includes a macro cell base station 1, asmall cell base station 3, and various examples of user equipment (UE),including a first mobile device 2 a, a wireless-connected car 2 b, alaptop 2 c, a stationary wireless device 2 d, a wireless-connected train2 e, a second mobile device 2 f, and a third mobile device 2 g.

Although specific examples of base stations and user equipment areillustrated in FIG. 1, a communication network can include base stationsand user equipment of a wide variety of types and/or numbers.

For instance, in the example shown, the communication network 10includes the macro cell base station 1 and the small cell base station3. The small cell base station 3 can operate with relatively lowerpower, shorter range, and/or with fewer concurrent users relative to themacro cell base station 1. The small cell base station 3 can also bereferred to as a femtocell, a picocell, or a microcell. Although thecommunication network 10 is illustrated as including two base stations,the communication network 10 can be implemented to include more or fewerbase stations and/or base stations of other types.

Although various examples of user equipment are shown, the teachingsherein are applicable to a wide variety of user equipment, including,but not limited to, mobile phones, tablets, laptops, IoT devices,wearable electronics, customer premises equipment (CPE),wireless-connected vehicles, wireless relays, and/or a wide variety ofother communication devices. Furthermore, user equipment includes notonly currently available communication devices that operate in acellular network, but also subsequently developed communication devicesthat will be readily implementable with the inventive systems,processes, methods, and devices as described and claimed herein.

The illustrated communication network 10 of FIG. 1 supportscommunications using a variety of cellular technologies, including, forexample, 4G LTE and 5G NR. In certain implementations, the communicationnetwork 10 is further adapted to provide a wireless local area network(WLAN), such as WiFi. Although various examples of communicationtechnologies have been provided, the communication network 10 can beadapted to support a wide variety of communication technologies.

Various communication links of the communication network 10 have beendepicted in FIG. 1. The communication links can be duplexed in a widevariety of ways, including, for example, using frequency-divisionduplexing (FDD) and/or time-division duplexing (TDD). FDD is a type ofradio frequency communications that uses different frequencies fortransmitting and receiving signals. FDD can provide a number ofadvantages, such as high data rates and low latency. In contrast, TDD isa type of radio frequency communications that uses about the samefrequency for transmitting and receiving signals, and in which transmitand receive communications are switched in time. TDD can provide anumber of advantages, such as efficient use of spectrum and variableallocation of throughput between transmit and receive directions.

In certain implementations, user equipment can communicate with a basestation using one or more of 4G LTE, 5G NR, and WiFi technologies. Incertain implementations, enhanced license assisted access (eLAA) is usedto aggregate one or more licensed frequency carriers (for instance,licensed 4G LTE and/or 5G NR frequencies), with one or more unlicensedcarriers (for instance, unlicensed WiFi frequencies).

As shown in FIG. 1, the communication links include not onlycommunication links between UE and base stations, but also UE to UEcommunications and base station to base station communications. Forexample, the communication network 10 can be implemented to supportself-fronthaul and/or self-backhaul (for instance, as between mobiledevice 2 g and mobile device 2 f).

The communication links can operate over a wide variety of frequencies.In certain implementations, communications are supported using 5G NRtechnology over one or more frequency bands that are less than 6Gigahertz (GHz) and/or over one or more frequency bands that are greaterthan 6 GHz. For example, the communication links can serve FrequencyRange 1 (FR1), Frequency Range 2 (FR2), or a combination thereof. In oneembodiment, one or more of the mobile devices support a HPUE power classspecification.

In certain implementations, a base station and/or user equipmentcommunicates using beamforming. For example, beamforming can be used tofocus signal strength to overcome path losses, such as high lossassociated with communicating over high signal frequencies. In certainembodiments, user equipment, such as one or more mobile phones,communicate using beamforming on millimeter wave frequency bands in therange of 30 GHz to 300 GHz and/or upper centimeter wave frequencies inthe range of 6 GHz to 30 GHz, or more particularly, 24 GHz to 30 GHz.

Different users of the communication network 10 can share availablenetwork resources, such as available frequency spectrum, in a widevariety of ways.

In one example, frequency division multiple access (FDMA) is used todivide a frequency band into multiple frequency carriers. Additionally,one or more carriers are allocated to a particular user. Examples ofFDMA include, but are not limited to, single carrier FDMA (SC-FDMA) andorthogonal FDMA (OFDMA). OFDMA is a multicarrier technology thatsubdivides the available bandwidth into multiple mutually orthogonalnarrowband subcarriers, which can be separately assigned to differentusers.

Other examples of shared access include, but are not limited to, timedivision multiple access (TDMA) in which a user is allocated particulartime slots for using a frequency resource, code division multiple access(CDMA) in which a frequency resource is shared amongst different usersby assigning each user a unique code, space-divisional multiple access(SDMA) in which beamforming is used to provide shared access by spatialdivision, and non-orthogonal multiple access (NOMA) in which the powerdomain is used for multiple access. For example, NOMA can be used toserve multiple users at the same frequency, time, and/or code, but withdifferent power levels.

Enhanced mobile broadband (eMBB) refers to technology for growing systemcapacity of LTE networks. For example, eMBB can refer to communicationswith a peak data rate of at least 10 Gbps and a minimum of 100 Mbps foreach user. Ultra-reliable low latency communications (uRLLC) refers totechnology for communication with very low latency, for instance, lessthan 2 milliseconds. uRLLC can be used for mission-criticalcommunications such as for autonomous driving and/or remote surgeryapplications. Massive machine-type communications (mMTC) refers to lowcost and low data rate communications associated with wirelessconnections to everyday objects, such as those associated with Internetof Things (IoT) applications.

The communication network 10 of FIG. 1 can be used to support a widevariety of advanced communication features, including, but not limitedto, eMBB, uRLLC, and/or mMTC.

FIG. 2 is a schematic diagram of one embodiment of a mobile device 800.The mobile device 800 includes a baseband system 801, a transceiver 802,a front end system 803, antennas 804, a power management system 805, amemory 806, a user interface 807, and a battery 808.

The mobile device 800 can be used communicate using a wide variety ofcommunications technologies, including, but not limited to, 2G, 3G, 4G(including LTE, LTE-Advanced, and LTE-Advanced Pro), 5G NR, WLAN (forinstance, WiFi), WPAN (for instance, Bluetooth and ZigBee), WMAN (forinstance, WiMax), and/or GPS technologies.

The transceiver 802 generates RF signals for transmission and processesincoming RF signals received from the antennas 804. It will beunderstood that various functionalities associated with the transmissionand receiving of RF signals can be achieved by one or more componentsthat are collectively represented in FIG. 2 as the transceiver 802. Inone example, separate components (for instance, separate circuits ordies) can be provided for handling certain types of RF signals.

The front end system 803 aids is conditioning signals transmitted toand/or received from the antennas 804. In the illustrated embodiment,the front end system 803 includes antenna tuning circuitry 810, poweramplifiers (PAs) 811, low noise amplifiers (LNAs) 812, filters 813,switches 814, and signal splitting/combining circuitry 815. However,other implementations are possible.

For example, the front end system 803 can provide a number offunctionalities, including, but not limited to, amplifying signals fortransmission, amplifying received signals, filtering signals, switchingbetween different bands, switching between different power modes,switching between transmission and receiving modes, duplexing ofsignals, multiplexing of signals (for instance, diplexing ortriplexing), or some combination thereof.

In certain implementations, the mobile device 800 supports carrieraggregation, thereby providing flexibility to increase peak data rates.Carrier aggregation can be used for both Frequency Division Duplexing(FDD) and Time Division Duplexing (TDD), and may be used to aggregate aplurality of carriers or channels. Carrier aggregation includescontiguous aggregation, in which contiguous carriers within the sameoperating frequency band are aggregated. Carrier aggregation can also benon-contiguous, and can include carriers separated in frequency within acommon band or in different bands.

The antennas 804 can include antennas used for a wide variety of typesof communications. For example, the antennas 804 can include antennasfor transmitting and/or receiving signals associated with a wide varietyof frequencies and communications standards.

In certain implementations, the antennas 804 support MIMO communicationsand/or switched diversity communications. For example, MIMOcommunications use multiple antennas for communicating multiple datastreams over a single radio frequency channel. MIMO communicationsbenefit from higher signal to noise ratio, improved coding, and/orreduced signal interference due to spatial multiplexing differences ofthe radio environment. Switched diversity refers to communications inwhich a particular antenna is selected for operation at a particulartime. For example, a switch can be used to select a particular antennafrom a group of antennas based on a variety of factors, such as anobserved bit error rate and/or a signal strength indicator.

The mobile device 800 can operate with beamforming in certainimplementations. For example, the front end system 803 can includeamplifiers having controllable gain and phase shifters havingcontrollable phase to provide beam formation and directivity fortransmission and/or reception of signals using the antennas 804. Forexample, in the context of signal transmission, the amplitude and phasesof the transmit signals provided to the antennas 804 are controlled suchthat radiated signals from the antennas 804 combine using constructiveand destructive interference to generate an aggregate transmit signalexhibiting beam-like qualities with more signal strength propagating ina given direction. In the context of signal reception, the amplitude andphases are controlled such that more signal energy is received when thesignal is arriving to the antennas 804 from a particular direction. Incertain implementations, the antennas 804 include one or more arrays ofantenna elements to enhance beamforming.

The baseband system 801 is coupled to the user interface 807 tofacilitate processing of various user input and output (I/O), such asvoice and data. The baseband system 801 provides the transceiver 802with digital representations of transmit signals, which the transceiver802 processes to generate RF signals for transmission. The basebandsystem 801 also processes digital representations of received signalsprovided by the transceiver 802. As shown in FIG. 2, the baseband system801 is coupled to the memory 806 of facilitate operation of the mobiledevice 800.

The memory 806 can be used for a wide variety of purposes, such asstoring data and/or instructions to facilitate the operation of themobile device 800 and/or to provide storage of user information.

The power management system 805 provides a number of power managementfunctions of the mobile device 800. In certain implementations, thepower management system 805 includes a PA supply control circuit thatcontrols the supply voltages of the power amplifiers 811. For example,the power management system 805 can be configured to change the supplyvoltage(s) provided to one or more of the power amplifiers 811 toimprove efficiency, such as power added efficiency (PAE).

As shown in FIG. 2, the power management system 805 receives a batteryvoltage from the battery 808. The battery 808 can be any suitablebattery for use in the mobile device 800, including, for example, alithium-ion battery.

FIG. 3 is a schematic diagram of a power amplifier system 860 accordingto one embodiment. The illustrated power amplifier system 860 includes abaseband processor 841, a transmitter/observation receiver 842, a poweramplifier (PA) 843, a directional coupler 844, front-end circuitry 845,an antenna 846, a PA bias control circuit 847, and a PA supply controlcircuit 848. The illustrated transmitter/observation receiver 842includes an I/Q modulator 857, a mixer 858, and an analog-to-digitalconverter (ADC) 859. In certain implementations, thetransmitter/observation receiver 842 is incorporated into a transceiver.

The baseband processor 841 can be used to generate an in-phase (I)signal and a quadrature-phase (Q) signal, which can be used to representa sinusoidal wave or signal of a desired amplitude, frequency, andphase. For example, the I signal can be used to represent an in-phasecomponent of the sinusoidal wave and the Q signal can be used torepresent a quadrature-phase component of the sinusoidal wave, which canbe an equivalent representation of the sinusoidal wave. In certainimplementations, the I and Q signals can be provided to the I/Qmodulator 857 in a digital format. The baseband processor 841 can be anysuitable processor configured to process a baseband signal. Forinstance, the baseband processor 841 can include a digital signalprocessor, a microprocessor, a programmable core, or any combinationthereof. Moreover, in some implementations, two or more basebandprocessors 841 can be included in the power amplifier system 860.

The I/Q modulator 857 can be configured to receive the I and Q signalsfrom the baseband processor 841 and to process the I and Q signals togenerate an RF signal. For example, the I/Q modulator 857 can includedigital-to-analog converters (DACs) configured to convert the I and Qsignals into an analog format, mixers for upconverting the I and Qsignals to RF, and a signal combiner for combining the upconverted I andQ signals into an RF signal suitable for amplification by the poweramplifier 843. In certain implementations, the I/Q modulator 857 caninclude one or more filters configured to filter frequency content ofsignals processed therein.

The power amplifier 843 can receive the RF signal from the I/Q modulator857, and when enabled can provide an amplified RF signal to the antenna846 via the front-end circuitry 845.

The front-end circuitry 845 can be implemented in a wide variety ofways. In one example, the front-end circuitry 845 includes one or moreswitches, filters, duplexers, multiplexers, and/or other components. Inanother example, the front-end circuitry 845 is omitted in favor of thepower amplifier 843 providing the amplified RF signal directly to theantenna 846. In the embodiment illustrated in FIG. 3, the front-endcircuitry 845 includes a duplexing circuit 100 which may include one ormore duplexers, as described below.

The directional coupler 844 senses an output signal of the poweramplifier 823. Additionally, the sensed output signal from thedirectional coupler 844 is provided to the mixer 858, which multipliesthe sensed output signal by a reference signal of a controlledfrequency. The mixer 858 operates to generate a downshifted signal bydownshifting the sensed output signal's frequency content. Thedownshifted signal can be provided to the ADC 859, which can convert thedownshifted signal to a digital format suitable for processing by thebaseband processor 841. Including a feedback path from the output of thepower amplifier 843 to the baseband processor 841 can provide a numberof advantages. For example, implementing the baseband processor 841 inthis manner can aid in providing power control, compensating fortransmitter impairments, and/or in performing digital pre-distortion(DPD). Although one example of a sensing path for a power amplifier isshown, other implementations are possible.

The PA supply control circuit 848 receives a power control signal fromthe baseband processor 841, and controls supply voltages of the poweramplifier 843. In the illustrated configuration, the PA supply controlcircuit 848 generates a first supply voltage V_(CC1) for powering aninput stage of the power amplifier 843 and a second supply voltageV_(CC2) for powering an output stage of the power amplifier 843. The PAsupply control circuit 848 can control the voltage level of the firstsupply voltage V_(CC1) and/or the second supply voltage V_(CC2) toenhance the power amplifier system's PAE.

The PA supply control circuit 848 can employ various power managementtechniques to change the voltage level of one or more of the supplyvoltages over time to improve the power amplifier's power addedefficiency (PAE), thereby reducing power dissipation.

One technique for improving efficiency of a power amplifier is averagepower tracking (APT), in which a DC-to-DC converter is used to generatea supply voltage for a power amplifier based on the power amplifier'saverage output power. Another technique for improving efficiency of apower amplifier is envelope tracking (ET), in which a supply voltage ofthe power amplifier is controlled in relation to the envelope of the RFsignal. Thus, when a voltage level of the envelope of the RF signalincreases the voltage level of the power amplifier's supply voltage canbe increased. Likewise, when the voltage level of the envelope of the RFsignal decreases the voltage level of the power amplifier's supplyvoltage can be decreased to reduce power consumption.

In certain configurations, the PA supply control circuit 848 is amulti-mode supply control circuit that can operate in multiple supplycontrol modes including an APT mode and an ET mode. For example, thepower control signal from the baseband processor 841 can instruct the PAsupply control circuit 848 to operate in a particular supply controlmode.

As shown in FIG. 3, the PA bias control circuit 847 receives a biascontrol signal from the baseband processor 841, and generates biascontrol signals for the power amplifier 843. In the illustratedconfiguration, the bias control circuit 847 generates bias controlsignals for both an input stage of the power amplifier 843 and an outputstage of the power amplifier 843. However, other implementations arepossible.

Example Duplexing Filter Circuits with Transmit Signal Cancellation

FIG. 4 is an example embodiment of a duplexer circuit 100 that can beused in an FDD or TDD radio front-end. As shown in FIG. 4, the duplexercircuit 100 is connected between a transmit (Tx) port 102, a receive(Rx) port 104, and an antenna (ANT) port 106. The transmit port 102includes one or more power amplifiers (PAs) 843 configured to amplify anRF signal and provide the amplified RF signal to an antenna connected tothe antenna port 106. Although not illustrated, the receive port 104 mayinclude one or more LNAs (e.g., the LNAs 812 of FIG. 2) and the antennaport 106 may include an antenna (e.g., the antenna 804 of FIG. 2 or theantenna 846 of FIG. 3).

The duplexer circuit 100 includes a duplexer 108 including a transmit(Tx) filter 108 a and a receive (Rx) filter 108 b coupled together at acommon node, such as an antenna node coupled to the antenna port 106. Anisolation path 107 is formed between the transmit port 102 and thereceive port 104. In some implementations, the duplexer 108 can beimplemented as a surface acoustic wave (SAW) duplexer, which can providerelatively wide bandwidth. However, this disclosure is not limitedthereto and in other implementations, the duplexer 108 can beimplemented as an LC filter or any other type of appropriate filtertechnology.

The transmit and receive filters 108 a and 108 b can be bandpass filtersthat respectively allow signals having the frequencies of the transmitand receive bands to reject or attenuate frequencies outside of therespective pass bands. Since the transmit and receive bands do not haveoverlapping frequencies, the RF transmit signals received from the poweramplifier can be attenuated by the combination of the transmit andreceive filters 108 a and 108 b such that the RF transmit signal isprevented from reaching the LNA on the receive port 104. That is, theduplexer 100 is configured to substantially block all frequencies alongthe isolation path 107 from the transmit port 102 to the receive port104.

However, in practice there may be a certain amount of leakage of the RFsignals through one or more of the transmit and receive filters 108 aand 108 b forming the duplexer circuit 100. In FDD and/or TDD radiofront-ends, performance can be limited due to leakage of noise and/orinterference through the duplexing filters 108 a and 108 b. Forinstance, the amplified RF signal received from the transmit port 102may leak through the duplexer 108 to the duplexer receive output portsand onto the receive port 104. The leakage of noise and interferencesthrough the duplexing filters 108 a and 108 b to the receive port 104can include all the gained up transceiver noise in the receive band, thepower amplifier 843 added noise in the receive band, as well as thetransmit carrier leakage that is provided from the transmit port 102 tothe transmit input of the duplexer 100 which can leak unintentionallyacross the duplexer 100 to the receive port 104. The transmit carrierleakage can result in a significant performance impact.

One technique for reducing leakage through the duplexer 100 is toprovide stronger attenuation of the duplexer 100 in order to reachdesired isolation values. Filter which provide stronger out-of-bandattenuation typically also have higher the insertion loss within-bandfor both the transmit and receive filters 108 a and 108 b. In addition,such filters once phased properly within the duplexer 100 itself alsoprovide better transmit-to-receive isolation. Single filters haveinvested in higher Q technology in order to achieve steeper skirts andbetter isolation, especially for comparatively difficult bands with arelatively narrow duplex gap and a relatively small frequency spacingbetween the transmit and receive bands.

Duplex spacing or duplex distance generally refers to the space betweenthe transmit and receive frequencies. As the duplex spacing decreases,the band gap (e.g., the space between the transmit and receive bands)also decreases. In 5G, the duplex spacing for many bands may be in therange of about 40-300 MHz, which may be relatively tight compared tolegacy network technologies.

Aspects of this disclosure relate to a duplexer circuit 100 that canreduce leakage from the transmit port 102 to the receive port 104without adjusting the out-of-band attenuation of the filters used in theduplexer circuit 100. FIG. 5 is an example embodiment of a duplexercircuit 100 that can be used in an FDD or TDD radio front-end inaccordance with aspects of this disclosure. The duplexer circuit 100 iscoupled to a transmit port 102, a receive port 104, and an antenna port106. The duplexer circuit 100 includes a transmit splitter 110, areceive splitter 112, and an antenna splitter 114, respectively coupledto the transmit port 102, the receive 104 port, and the antenna port106.

The duplexer circuit 100 further includes a first phase shifter 116, asecond phase shifter 118, a third phase shifter 120, a first duplexer122, and a second duplexer 124. In addition, a first isolation path 107and a second isolation path 109 are formed between the transmit port 102and the receive port 104. In certain implementations, each of the firstto third phase shifters 116-120 is configured to provide a substantially90° phase shift. The first and second duplexers 122 and 124 may besubstantially matched and each include a transmit filter 122 a, 124 aand a receive filter 122 b, 124 b.

As shown in FIG. 5, the use of the splitters 110-114 provides parallelpaths between each of the transmit port 102, the receive port 104, andthe antenna port 106. The first to third phase shifters 116-120 arelocated such that the parallel paths cancel RF signals between thetransmit port 102 and the receive port 104 and sum coherently betweenthe antenna port 106 and each of the transmit and receive ports 102 and104. For example, the first and second splitters 110 and 112, the firstand second phase shifters 116 and 118, and the first and secondduplexers 122 and 124 form the first and second isolation paths 107 and109. In detail, the first and second phase shifter 116 and 118 are bothformed on the first isolation path 107 while no phase shift is appliedon the second isolation path 109. Thus, the first isolation path 107provides a 180° phase shift compared to the second isolation path 109such that the RF leakage signal along the first isolation path 107cancels the RF leakage signal along the second isolation path 109. Byproviding cancelation of the RF leakage signals along the first andsecond isolation paths 107 and 109, the isolation between the transmitport 102 and the receive port 104 is increased without altering theconstruction of the first and second duplexers 122 and 124.

The duplexer circuit 100 further provides constructive summing of thepaths between the transmit port 102 and the antenna port 106, as well asbetween the antenna port 106 and the receive port 104. For example, thefirst phase shifter 116 and the third phase shifter 120 are placed onrespective paths such that the RF signals transmitted on the parallelpaths between the transmit port 102 and the antenna port 106 are bothphase shifted by 90° and thus sum constructively. Similarly, the secondphase shifter 118 and the third phase shifter 120 are placed onrespective paths such that the RF signals transmitted on the parallelpaths between the antenna port 106 and the receive port 102 are bothphase shifted by 90° and thus sum constructively.

Aspects of this disclosure which provide parallel isolation paths 107and 109 for which one of the paths 107 and 109 is phase shifted by 180°can provide broadband active cancellation that can greatly improve thedegradation of the reference sensitivity for the partnered band. As usedherein, reference sensitivity generally refers to the sensitivity at thereceiver even when the transmitter is off. The active transmitcancellation described herein can also potentially relax the overallfilter requirements of each of the first and second duplexers 122 and124, even for relatively small duplex spacing scenarios. Reflection fromantenna port 106 mismatch may degrade the effectiveness of thecancellation, however, the cancellation is optimized with higherout-of-band attenuations. According to aspects of this disclosure, theduplexer circuit 100 may be a band-dedicated implementation.

While the use of a duplexer circuit 100 such as that of FIG. 5 mayinvolve a larger area and/or cost compared to other techniques, theactive canceling of leakage signals using matched duplexers 122 and 124enable greater improved performance in bands that are previously onlywell addressed by extremely expensive (and potentially large as well)duplexers in different technologies. Thus, aspects of this disclosurecan allow a lower cost and smaller duplexer circuit 100 approach to beused with higher performance for reference sensitivity.

FIG. 6 illustrates an embodiment of a splitter 110 which can be used inaccordance with aspects of this disclosure. In particular, the splitter110 is a passive power splitter that includes an impedance 126 (e.g., adissipation resistor) connected between the two output legs of thesplitter 110. In certain implementations, the splitter 110 can beembodied as a Wilkinson power splitter. In particular, a simpleT-junction may function well if both sides are balanced, however, if theimpedances of the legs of the T-junction are not matched, cancellationmay not be as good. The use of a splitter 110 such as a Wilkinson powersplitter can address this issue. The impedance 126 can dissipateimpedance match between the two branches of the splitter 110.

FIG. 7 is another example embodiment of a duplexer circuit 100 that canbe used in an FDD or TDD radio front-end in accordance with aspects ofthis disclosure. Similar to FIG. 5, the duplexer circuit 100 of FIG. 7is coupled to a transmit port 102, a receive port 104, and an antennaport 106. The duplexer circuit 100 includes a transmit hybrid splitter130, an antenna hybrid splitter 132, a receive hybrid splitter 134,first to third resistors 136-140, a first duplexer 142, and a secondduplexer 144. The transmit, antenna, and receive hybrid splitters130-134 are respectively connected to the transmit, antenna, and receiveports 102-106. In addition, each of the transmit, antenna, and receivehybrid splitters 130-134 are connected to ground via a corresponding oneof the first to third resistors 136-140.

The transmit, antenna, and receive hybrid splitters 130-134 may beimplemented as 90° 3 dB hybrid splitters (for example, the hybridsplitters 130-134 may be implemented as hybrid baluns). With referenceto the transmit hybrid splitter 130 as an example, the transmit hybridsplitter 130 receives an RF signal from the transmit port 102 as aninput and splits the RF signal into two RF signals, a first one of thesplit RF signals has no phase shift and a second one of the split RFsignals has a 90° phase shift. The two RF signals output from thetransmit hybrid splitter 130 are provided to the first and secondduplexers 142.

Any leakage from the first split RF signal (e.g., having no phase shift)through the first duplexer 142 is applied to the third hybrid splitter134 and undergoes no phase shift for the portion that is split to thereceive port 106. Further, any leakage from the second split RF signal(e.g., having a 90° phase shift) through the second duplexer 144 isapplied to the third hybrid splitter 134 and undergoes a further 90°phase shift for the portion that is split to the receive port 106. Thus,the leakage signals from the first and second split RF signals have aphase shift of 180° with respect to each other, and thus, cancel at thereceive port 106.

The connections between the first to third hybrid splitters 130-134 andthe first and second duplexers 142 and 144 provide for constructiveinterference between the transmit port 102 and the antenna port 104 aswell as between the antenna port 104 and the receive port 106. Portionsof the signals split via any one of the first to third hybrid splitters130-134 which are not used for either cancelling leaking or constructiveinterference of the RF signals are grounded via the first to thirdresistors 136-140.

By providing active RF leakage cancellation between the transmit port102 and the receive port 106, the FIG. 7 implementation may have thesame advantages as discussed above in connection with the FIG. 6implementation.

FIG. 8 is a flowchart that provides a method for improved RF leakagecancellation for a duplexer circuit used in a radio front-end inaccordance with aspects of this disclosure. The method 200 can beperformed using the duplexer circuit 100 of either FIG. 6 or FIG. 7.

The method 200 starts at block 201. At block 202, the method 200involves outputting first and second radio frequency transmit signalsonto respective first and second parallel transmit paths extendingbetween a power amplifier and an antenna. At block 204, the method 200involves applying a first phase shift to the first radio frequencytransmit signal between the power amplifier and a first duplexer on thefirst transmit path. At block 206, the method 200 involves outputtingfirst and second radio frequency receive signals onto respective firstand second parallel receive paths extending between the antenna and areceive splitter. At block 208, the method 200 involves applying asecond phase shift to the first radio frequency receive signal betweenthe antenna and a second duplexer on the first receive path. At block210, the method 200 involves applying a third phase shift to the secondradio frequency receive signal between the first duplexer and thereceive splitter on the second receive path. The method 200 ends atblock 212.

Further Example Duplexing Filter Circuits with Transmit SignalCancellation

Frequency division duplex (FDD) operation involves concurrent transmitand receive, separated in frequency offset of the duplex spacing and thelow noise receive path is protected from the transmit impairments by theisolation provided by the filter isolation of the duplexer. Thisisolation may come at the cost of insertion loss in the transmit signal(e.g., higher DC consumption and lower power capability at the antenna)and in the receive signal (degraded sensitivity even when thetransmitter is off, so-called “reference sensitivity”). As the transmitpower levels increase and transmit channel bandwidths increase, thesechallenges to protect the receiver from the transmit impairments becomesmore difficult.

Transmit impairments include but are not limited to: 1) transmit leakageof modulated carrier power, 2) adjacent channel leakage ratio (ACLR) andspectral emissions regrowth falling directly onto the active receivechannel, 3) ACLR that leaks through the transmit-to-receive isolation(e.g., mid-duplex gap isolation) in the form of a concentrated highamplitude intermodulation distortion (IMD) spurious, 4) receive bandnoise (white noise) generated in the power amplifier, 5) receive bandnoise (white noise) generated by the transceiver gained up by the poweramplifier, 6) reverse intermodulation created at the power amplifieroutput from back-injected blocker mixing with the forward transmitcarrier power to produce IMD that can fall onto the receive channel, and7) farther offset harmonics or general spurious that can additionallydegrade the active receive.

As described above, one technique for reducing leakage through theduplexer 100 involves providing stronger attenuation and isolation ofthe transmit-to-receive properties of the duplex filter (e.g., see theduplexer 108 of FIG. 4), which come at some trade-off and sacrifice todegrade (increase) the insertion loss of the transmit and receive paths.This technique may involve leveraging phase cancellation and brute forceisolation properties of the duplexer to address the attenuation of thetransmit impairments.

Even using stronger attenuation, there may be unavoidable transmitterpower leak. Relatively high power blockers may be out of the low-noiseamplifier intended pass band. Further, the typical transmit power levelmay be so large as to saturate the low-noise amplifier. One or more ofALCR emissions, white noise out of band, and noise components may falldirectly into the active receive channel. In addition, the non-linearityof the power amplifier can create spectral regrowth.

FIG. 9 is an example embodiment of a duplexer circuit 300 that can beused in an FDD or TDD radio front-end. As shown in FIG. 9, the duplexercircuit 300 is connected between a power amplifier (PA) 302 connected toa transmit port 301, a low-noise amplifier (LNA) 304 connected to areceive port 305, and an antenna 306. The power amplifier 302 isconfigured to amplify an RF signal received from the transmit port 301and provide the amplified RF signal to the antenna 306 via the duplexercircuit 300. The low-noise amplifier 304 is configured to receive an RFsignal from the antenna 306 via the duplexer circuit 300.

The duplexer circuit 300 includes a duplexer 308 including a transmitfilter 308A and a receive filter 308B, which are respectively coupled tothe power amplifier 302 and the low-noise amplifier 304. The transmitfilter 308A and the receive filter 308B are coupled together at a commonnode, such as an antenna node coupled to the antenna 306. In someimplementations, the duplexer 308 can be implemented as a surfaceacoustic wave (SAW) duplexer, which can provide relatively widebandwidth. However, this disclosure is not limited thereto and in otherimplementations, the duplexer 308 can be implemented as an LC filter orany other type of appropriate filter technology.

As shown in FIG. 9, there may be a certain amount of leakage 320 throughthe duplexer 308 from the power amplifier 302 to the low-noise amplifier304. The transmit carrier leakage through the duplexer 308 can result ina significant performance impact. Some amount of leakage 320 may bepresent no matter how good the rejection of the duplexer 308. Thus,aspects of this disclosure relate to techniques for cancelling theleakage 320 from the transmit port 301 and the power amplifier 302 tothe low-noise amplifier 304 and the receive port 305.

Aspects of this disclosure provide a matched path for the transmitleakage 320, and does not require the use of a receive channel or theantenna based out of band blocker. By amplitude and phase adjusting thematched filter leakage 320 path, cancellation of these unwantedimpairments can be provided. Thus, aspects of this disclosure providefor enhanced cancellation of substantially all transmit impairmentsdescribed herein, and can effectively provide much lower receivede-sense as a result, with less impact to insertion loss and even lowtransmit power performance.

Aspects of this disclosure can address one or all of theabove-identified issues. FIG. 10 is an example embodiment of a duplexercircuit 300 that can be used in an FDD or TDD radio front-end inaccordance with aspects of this disclosure. With reference to FIG. 10,the duplexer circuit 300 is connected between a power amplifier 302connected to a transmit port 301; a first low-noise amplifier 304A, aphase shifter 312, a second low-noise amplifier 304B, and a splitter 314connected to a receive port 305; and an antenna 306. The power amplifier302 is configured to amplify an RF signal received from the transmitport 301 and provide the amplified RF signal to the antenna 306 via theduplexer circuit 300. The first low-noise amplifier 304A is configuredto receive an RF signal from the antenna 306 via the duplexer circuit300. Further details on the functionality of the first and secondlow-noise amplifiers 304A and 304B, the phase shifter 312, and thesplitter 314 are provided below.

The duplexer circuit 300 includes a first transmit filter 308A and afirst receive filter 308B, which may be substantially similar to thetransmit and receive filters 308A and 308B of FIG. 9. The duplexercircuit 300 of FIG. 10 further includes a second receive filter 310B anda second transmit filter 310A which are electrically coupled to providea second path 322 between the transmit port 301 and the receive port305. The second path 322 (e.g., including the second receive filter 310Band a second transmit filter 310A) is substantially matched to a primarypath which includes the first transmit filter 308A and the first receivefilter 308B. Thus, the leakage current 320 flowing through the firsttransmit filter 308A and the first receive filter 308B may besubstantially matched by a second leakage current flowing through thesecond path 322.

The first low-noise amplifier 304A, the phase shifter 312, the secondlow-noise amplifier 304B, and the splitter 314 are arranged between theduplexer circuit 300 and the receive port 305 and are configured tocancel the leakage current 320 and the second leakage current. Indetail, the phase shifter 312 can be configured to shift the secondleakage current by substantially 180° and the first and second low-noiseamplifiers 304A and 304B are configured to respectfully amplify thefirst and second leakage currents by the same amount. However, in otherembodiments, the phase shifter 312 may be configured to provide adifferent amount of phase shift or may be omitted from the circuit asdescribed herein.

Finally, the splitter 314 (functioning as a mixer) is configured tocombine the amplified leakage currents, which results in cancellationsince the two leakage currents are phase offset by 180° and havesubstantially the same amplitude.

While a certain amount of leakage current may also be present betweenthe transmit port 301 and the antenna 306 as well as between the antenna306 and the receive port 305, this leakage current may be insignificantcompared to the desired RF signals being communicated. For example, anRF receive signal received at the antenna 306 is provided to the firstlow noise amplifier 304A via the first receive filter 308B. An RFreceive leakage signal must travel through the first transmit filter308A, the second receive filter 310B, and the second transmit filter310A before arriving at the phase shifter 312. Because the pass bands ofthese three filters do not overlap, the amplitude of the RF receiveleakage signal will be significantly lower than the RF receive signalreceived at the first low noise amplifier 304A, and thus, thesignal-to-noise ratio of the RF receive signal is not significantlyaffected by the RF receive leakage current. An RF transmit signalprovided from the transmit port 301 to the antenna 306 is similarly notsignificantly affected by an RF transmit leakage signal.

FIGS. 11A and 11B provide example embodiments of circuit configurationswhich can be used to connect the receive port 305 to the duplexercircuit 300 of FIG. 10 in accordance with aspects of this disclosure.With reference to the embodiment illustrated in FIG. 11A, the splitter314 can include a balun 316 having a first loop connected between thereceive port 305 and ground and a second loop connected between thefirst and second low-noise power amplifiers 304A and 304B. Because thebalun 316 is configured to receive a balance input, the leakage signalsprovided by the first and second low-noise power amplifiers 304A and304B do not need to be phase offset in order for the balun 316 to cancelthe matched leakage signals. Thus, the phase shifter 312 of the FIG. 11Aembodiment can be configured to provide no phase shift (e.g., 0° phaseshift) or can be omitted from the circuit such that the second low-noisepower amplifier 304B is directly connected to the duplexer circuit 300.

With reference to the embodiment illustrated in FIG. 11B, the splitter314 can include a passive power splitter 318 (e.g., such as the splitter110 illustrated in FIG. 6) configured to function as a mixer thatcombines the RF signals respectively received from the first and secondlow-noise amplifiers 304A and 304B. For example, the power splitter 318can include an impedance 319 coupled between the inputs connected to thefirst and second low-noise amplifiers 304A and 304B. In the FIG. 11Bembodiment, the phase shifter 312 can be configured to provide about a180° phase shift such that the leakage currents input into the splitter312 are substantially cancelled before reaching the receive port 305.

FIG. 12 is another example embodiment of a duplexer circuit 300 that canbe used in an FDD or TDD radio front-end in accordance with aspects ofthis disclosure. Similar to the FIG. 10 embodiment, the duplexer circuit300 is connected between a power amplifier 302 connected to a transmitport 301; a first low-noise amplifier 304A, a phase shifter 312, asecond low-noise amplifier 304B, and a splitter 314 connected to areceive port 305; and an antenna 306. The power amplifier 302 isconfigured to amplify an RF signal received from the transmit port 301and provide the amplified RF signal to the antenna 306 via the duplexercircuit 300. The first low-noise amplifier 304A is configured to receivean RF signal from the antenna 306 via the duplexer circuit 300.

In contrast to the FIG. 10 embodiment, the duplexer 300 of FIG. 12includes a transmit filter 308A, a first receive filter 308B, and asecond receive filter 310B, omitting the second transmit filter 310A ofFIG. 10. The second receive filter 310B is coupled to the phase shifter312. Although a second leakage current flowing through the secondreceive filter 310B does not flow through a second transmit filter 310A,the second leakage current may still have substantially the sameamplitude as a first leakage current flowing through the transmit filter308A and the receive filter 308B. Thus, the first low-noise amplifier304A, the phase shifter 312, the second low-noise amplifier 304B, andthe splitter 314 can be configured to cancel the first and secondleakage currents before the leakage currents reach the receive port 305.In some embodiments, splitter 314 can be implemented using one of theembodiments of FIGS. 11A and 11B.

Example Duplexing Filter Circuits with EM Coupling Cancellation

FIGS. 13A and 13B illustrate yet another example embodiment of aduplexer circuit 300 that can be used in an FDD or TDD radio front-endin accordance with aspects of this disclosure. In particular, FIG. 13Aillustrates the duplexer 300 with a circuit diagram oriented similar tothat of FIGS. 10 and 12, while FIG. 13B illustrates an alternative viewof the circuit diagram for the duplexer 300 of FIG. 13A.

With reference to FIGS. 13A and 13B, the duplexer circuit 300 isconnected between a power amplifier 302 connected to a transmit port301; a first low-noise amplifier 304A, a second low-noise amplifier304B, and a splitter 314 connected to a receive port 305; and an antenna306. The power amplifier 302 is configured to amplify an RF signalreceived from the transmit port 301 and provide the amplified RF signalto the antenna 306 via the duplexer circuit 300. The first low-noiseamplifier 304A is configured to receive an RF signal from the antenna306 via the duplexer circuit 300.

FIG. 13A further illustrates an embodiment of the splitter 314, whichcan be combined with any other embodiment disclosed herein. In thisembodiment, the splitter 314 includes a first phase shifter 330, asecond phase shifter 332, and a mixer 334. The first phase shifter 330can be configured to apply a positive 45° phase shift and the secondphase shifter 332 can be configured to apply a negative 45° phase shift.Accordingly, the two signals receives at the mixer 334 have a relativephase shift of 180° and are cancelled before reaching the receive port305.

The duplexer 300 includes a first transmit filter 308A, a first receivefilter 308B, a second transmit filter 310A, a second receive filter310B, a first impedance 350A and a second impedance 350B. In theembodiment of FIGS. 13A and 13B, the filters 308A, 308B, 310A, and 310Bare connected by conductive traces. The filters 308A, 308B, 310A, and310B and conductive traces are arranged in order to match radiativecoupling of EM therebetween. The first and second impedances 350A and350B can be configured to improve impedance and loading effects.

With reference to FIG. 13A, five nodes 1-5 are illustrated at points onthe conductive trances. A first EM coupling 340 may be formed betweennode 1 and node 4 and a second EM coupling 342 may be formed betweennode 1 and node 3. A first leakage current 344 and a second leakagecurrent 346 from the transmit port 301 to the receive port 305 are alsoshown in FIG. 13A.

In order to substantially match the first and second EM couplings 340and 342, the duplexer 300 may be physically laid out as shown in FIG.13B. As shown in FIG. 13B, the filters 308A, 308B, 310A, and 310B,conductive traces, and first and second impedances 350A and 350B arearranged substantially symmetrically such that the first and second EMcouplings 340 and 342 will substantially cancel at the splitter 314before arriving at the receive port 305.

In some embodiments, the first impedance 350A may include a shuntinductor, which is applied at the common port 2 of the first transmitfilter 308A and the first receive filter 308B. The shunt inductortogether with a capacitor for the first transmit filter 308A canfunction as a parallel LC circuit, which may be resonant over a firstfrequency range. The LC circuit may be designed to function as an opencircuit at frequencies of interest. The second impedance 350B isconfigured to substantially match the first impedance 350A. In someimplementations, matching the first and second impedances 350A and 350Bmay involve tuning one or more of the first and second impedances 350Aand 350B to obtain a sufficient match therebetween. That is, one or moreof the first and second impedances 350A and 350B may be tunable toimprove the EM coupling cancelation of the duplexer 300. In someembodiments, one or more of the first and second impedances 350A and350B may have a programmable impedance via a switched parallel inductorcoupled to ground.

Example Diplexing Filter Circuits with Signal Cancellation BetweenDifferent Communication Technologies

FIG. 14 is an example embodiment of a diplexer circuit 400 that can beused to couple two different communication technologies to an antenna inaccordance with aspects of this disclosure. The diplexer circuit 400 ofFIG. 14 is coupled to a cellular port 402, a Wi-Fi port 404, and anantenna port 406. Thus, the diplexer circuit 400 is configured toselectively connect one of the cellular port 402 and the Wi-Fi port 404to the antenna port 406 for wireless communication. The diplexer circuit400 is further connected to ground via a plurality of resistors 408,410, and 412.

The diplexer circuit 400 includes first and second diplex filters 414and 416, a cellular hybrid splitter 418, a Wi-Fi hybrid splitter 420,and an antenna hybrid splitter 422. The cellular, Wi-Fi, and antennahybrid splitters 418-422 are respectively connected to the cellular,Wi-Fi, and antenna ports 402-406. In addition, each of the cellular,Wi-Fi, and antenna hybrid splitters 418-422 are connected to ground viaa corresponding one of the first to third resistors 408-412.

Similar to the FIG. 7 embodiment, the cellular, Wi-Fi, and antennahybrid splitters 418-422 may be implemented as 90° 3 dB hybrid splitters(for example, the hybrid splitters 418-422 may be implemented as hybridbaluns). The diplexer circuit 400 is configured to reduce leakagesignals between the cellular port 402 and the Wi-Fi port 404 byproviding two paths therebetween with the leakage signals on the twopaths cancelling each other.

With reference to the cellular hybrid splitter 418 as an example, thecellular hybrid splitter 418 receives an RF signal from the cellularport 402 as an input and splits the RF signal into two RF signals. Afirst one of the split RF signals has no phase shift and is provided tothe first diplexer 414 and a second one of the split RF signals has a90° phase shift and is provided to the second diplexer 416.

Any leakage from the first split RF signal (e.g., having no phase shift)through the first diplexer 142 is applied to the Wi-Fi hybrid splitter420 and undergoes no phase shift for the portion that is split to theWi-Fi port 404. Further, any leakage from the second split RF signal(e.g., having a 90° phase shift) through the second diplexer 422 isapplied to the Wi-Fi hybrid splitter 420 and undergoes a further 90°phase shift for the portion that is split to the Wi-Fi port 404. Thus,the leakage signals from the first and second split RF signals have aphase shift of 180° with respect to each other, and thus, cancel at theWi-Fi port 404. Signal originating from the Wi-Fi port 404 undergo asimilar cancellation on the path to the cellular port 402.

The connections between the cellular, Wi-Fi, and antenna hybridsplitters 418-422 and the first and second diplexers 414 and 416 providefor constructive interference between the cellular port 402 and theantenna port 406 as well as between the Wi-Fi port 404 and the antennaport 406. Portions of the signals split via any one of the cellular,Wi-Fi, and antenna hybrid splitters 418-422 which are not used foreither cancelling leaking or constructive interference of the RF signalsare grounded via the first to third resistors 408-412.

By providing active RF leakage cancellation between the cellular port402 and the Wi-Fi port 410, the FIG. 14 implementation may have the sameadvantages as discussed above in connection with the implementations ofFIGS. 6 and 7.

The embodiment of FIG. 14 can address limited isolation and impedancetermination challenges that limit low loss diplexing (impedance loadingof one path depends on impedance loading other path, which can result in“suck-outs” and poor impedance loading depending on frequency-dependentphase of the complex terminations) by employing balanced configurationthat substantially guarantees 50 Ohm. In other implementations, thediplexer isolation may be relaxed, which results in this problem andeventually the diplexer is unusable due to this variability in theapplication.

The embodiment of FIG. 14 can also enhance the isolation between thecellular port 402 and the Wi-Fi port 404 by the isolation property ofthe hybrid splitters 418-422 (e.g., which may have 20-25 dB isolation).The first to third resistors 408-412 may provide a substantially idealmatch for the dixplers 414 and 416 to the antenna 406. The isolation maybe above a threshold within a given range of the band edge for thetransmit and receive bands. The transmit leakage and receive band can besuppressed in both directions (e.g., from cellular to Wi-Fi and fromWi-Fi to cellular). By providing this cancellation, aspects of thisdisclosure can provide higher isolation with a difficult impedanceloading vs. out of band attenuation trade-off than compared to otherapproaches.

When the bandwidth of the hybrid splitters 418-422 is wider than athreshold value, the second harmonics can also be phase cancelled inboth directions (e.g., from cellular to Wi-Fi and from Wi-Fi tocellular).

One example implementation is between band B40 (e.g., 2.3-2.4 GHz) andB41 (e.g., 2.496-2.69 GHz) for LTE for the cellular signal and 2.4 GHzWi-Fi that is in between B40 and B41 (e.g., 2.403-2.495 GHz). Aspects ofthis disclosure enables 20-25 dB enhanced isolation for this extremelychallenging coexistence case, and potentially greatly relaxes the filterattenuation required (e.g., less impedance loading).

According to aspects of this disclosure, the termination 402-406 may beused for sensing the reflected/non-coherent desired signals, andpotentially used in further signal cancellation schemes for advantage incoexistence by the radio.

FIG. 15 is another example embodiment of a diplexer circuit 400 that canbe used to couple two different communication technologies to twoantennas in accordance with aspects of this disclosure. The diplexercircuit 400 of FIG. 15 is coupled to a first cellular port 402A, asecond cellular port 402B, a first Wi-Fi port 404A, a second Wi-Fi port404B, an first antenna port 406A, and a second antenna port 406B. Thediplexer circuit 400 is configured to selectively connect one of thefirst cellular port 402A and the first Wi-Fi port 404A to the firstantenna port 406A as well as one of the second cellular port 402B andthe second Wi-Fi port 404B to the second antenna port 406B.

The communication between the first cellular port 402A and the firstWi-Fi port 404A to the first antenna port 406A is substantially similarto that described above in connection with FIG. 14. In addition, thecommunication between the second cellular port 402B and the second Wi-Fiport 404B to the second antenna port 406B function similarly to thecommunication between the first ports 402A, 404A, and 406A. Further,cross communications between the first ports 402A, 404A, and 406A andthe second ports 402B, 404B, and 406B are substantially insignificant byproviding cancellation of any leakage signals from the firstcellular/Wi-Fi ports 402A, 404A, and 406A and the second antenna 406B aswell as cancellation of any leakage signals from the secondcellular/Wi-Fi ports 402B, 404B, and 406B and the first antenna 406A.

In implementations of the FIG. 15 embodiment, by driving the additionalports of the hybrid splitters 418-422 compared to FIG. 14, additionalsignals can be routed through the diplexers 414 and 422 concurrently,and substantially optimally with much less loss to multiple antennaconfigurations. This can enable low loss carrier aggregation of closelyspaced bands and channels to multiple antennas with the afore describedbenefits of FIG. 14 of high isolation and lower insertion loss. In oneexample, the impedance presented to the ports 402A-406B may besubstantially ideal if close to 50 Ohm to preserve the isolationcharacteristics of the hybrid splitters 418-422 and balancedarchitecture.

FIG. 16 is a flowchart that provides a method for improved RF leakagecancellation for a duplexer circuit used in a radio front-end inaccordance with aspects of this disclosure. The method 500 can beperformed using the duplexer circuit 300 of any one of either FIGS. 10,13A, and 13B.

The method 500 starts at block 501. At block 502, the method 500involves outputting a first radio frequency transmit signal to a firsttransmit filter positioned between a power amplifier and an antenna. Atblock 504, the method 500 involves amplifying the first radio frequencytransmit signal at a first low-noise amplifier received from the firsttransmit filter via a first receive filter. At block 506, the method 500involves outputting a second radio frequency transmit signal to acancellation path including a second receive filter and a secondtransmit filter. At block 508, the method 500 involves applying a phaseshift to one or both the second radio frequency transmit signal receivedfrom the cancellation path. At block 510, the method 500 involvesamplifying the phase shifted second radio frequency at a secondlow-noise amplifier. The method 500 ends at block 512.

FIG. 17 is a flowchart that provides a method for improved RF leakagecancellation for a diplexer circuit in accordance with aspects of thisdisclosure. The method 600 can be performed using the diplexer circuit400 of any one of either FIGS. 14 and 15.

The method 600 starts at block 601. At block 602, the method 600involves outputting first and second radio frequency transmit signalsonto respective first and second parallel communication paths extendingbetween a first radio frequency transceiver terminal and an antenna. Atblock 604, the method 600 involves applying a first phase shift to thefirst radio frequency transmit signal between the first radio frequencyterminal and a first diplexer on the first communication path. At block606, the method 600 involves outputting third and fourth radio frequencytransmit signals onto respective third and fourth parallel communicationpaths extending between a second radio frequency transceiver and theantenna. At block 608, the method 600 involves applying a second phaseshift to the second radio frequency transmit signal between the antennaand a second diplexer on the second communication path. At block 610,the method 600 involves applying a third phase shift to the first radiofrequency transmit signal between the first diplexer and the secondradio frequency transceiver on the third communication path. The method600 ends at block 612.

CONCLUSION

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Likewise, the word “connected”, as generally used herein, refers to twoor more elements that may be either directly connected, or connected byway of one or more intermediate elements. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, shall refer to this application as a whole and not toany particular portions of this application. Where the context permits,words in the above Detailed Description using the singular or pluralnumber may also include the plural or singular number respectively. Theword “or” in reference to a list of two or more items, that word coversall of the following interpretations of the word: any of the items inthe list, all of the items in the list, and any combination of the itemsin the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “can,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/orstates are included or are to be performed in any particular embodiment.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A diplexer circuit comprising: first and secondradio frequency transceiver terminals and a first antenna terminal;first and second parallel communication paths extending between thefirst radio frequency transceiver terminal and the first antennaterminal, and third and fourth parallel communication paths extendingbetween the second radio frequency transceiver terminal and the firstantenna terminal; a first phase shifter configured to apply a firstphase shift to a first radio frequency transmit signal between the firstradio frequency transceiver terminal and a first diplexer on the firstcommunication path, a second phase shifter configured to apply a secondphase shift to a second radio frequency transmit signal between thefirst antenna terminal and a second diplexer on the second communicationpath, and a third phase shifter configured to apply a third phase shiftto the first radio frequency transmit signal between the first diplexerand the second radio frequency transceiver terminal on the thirdcommunication path.
 2. The diplexer circuit of claim 1 wherein thesecond phase shifter is further configured to coherently sum the firstand second radio frequency transmit signals, and wherein the secondphase shifter is further configured to coherently sum third and fourthradio frequency transmit signals received from the second radiofrequency transceiver terminal.
 3. The diplexer circuit of claim 1wherein the first phase shifter is further configured to destructivelycancel leakage of third and fourth radio frequency transmit signalsreceived from the second radio frequency transceiver terminal, andwherein the third phase shifter is further configured to destructivelycancel leakage of the first and second radio frequency transmit signalsreceived from the first radio frequency transceiver terminal.
 4. Thediplexer circuit of claim 1 wherein the first phase shifter includes afirst hybrid transmit splitter, the second phase shifter includes asecond hybrid receive splitter, and the third phase shifter includes athird hybrid antenna splitter.
 5. The diplexer circuit of claim 1further comprising: a third radio frequency transceiver terminal coupledto the first phase shifter; a fourth radio frequency transceiverterminal coupled to the third phase shifter; a second antenna terminalcoupled to the second phase shifter; fifth and sixth parallelcommunication paths extending between the third radio frequencytransceiver terminal and the second antenna terminal; and seventh andeighth parallel communication paths extending between the fourth radiofrequency transceiver terminal and the second antenna terminal.
 6. Thediplexer circuit of claim 5 wherein the first phase shifter is furtherconfigured to apply a fourth phase shift to a third radio frequencytransmit signal between the third radio frequency terminal and the firstdiplexer on the fifth communication path, wherein the second phaseshifter is further configured to apply a fifth phase shift to a fourthradio frequency transmit signal between the third antenna terminal andthe second diplexer on the sixth communication path, and the third phaseshifter is further configured to apply a sixth phase shift to the thirdradio frequency transmit signal between the first diplexer and thesecond radio frequency transceiver on the seventh communication path. 7.The diplexer circuit of claim 1 wherein the first radio frequencytransceiver terminal is configured to communicate via a cellular signal,and wherein the second radio frequency transceiver terminal isconfigured to communicate via a Wi-Fi signal.
 8. The diplexer circuit ofclaim 1 wherein the first phase shifter and the third phase shifter areconfigured to provide a phase shift of about 180° to the first radiofrequency transmit signal.
 9. The diplexer circuit of claim 1 whereinthe first phase shifter and the second phase shifter are configured toprovide a phase shift of about 90° to each of the first and second radiofrequency transmit signals.
 10. The diplexer circuit of claim 1 whereinthe third phase shifter is configured to apply a fourth phase shift to asecond radio frequency transmit signal between the second radiofrequency terminal and the first diplexer on the third communicationpath, and wherein the second phase shifter is configured to apply afifth phase shift to a fourth radio frequency transmit signal betweenthe first antenna terminal and the first diplexer on the fourthcommunication path.
 11. The diplexer circuit of claim 10 wherein thesecond phase shifter and the third phase shifter are configured toprovide a phase shift of about 90° to each of the third and fourth radiofrequency transmit signals.
 12. A method of diplexing radio frequencysignals, the method comprising: outputting first and second radiofrequency transmit signals onto respective first and second parallelcommunication paths extending between a first radio frequencytransceiver terminal and an antenna; applying a first phase shift to thefirst radio frequency transmit signal between the first radio frequencyterminal and a first diplexer on the first communication path;outputting third and fourth radio frequency transmit signals ontorespective third and fourth parallel communication paths extendingbetween a second radio frequency transceiver terminal and the antenna;applying a second phase shift to the second radio frequency transmitsignal between the antenna and a second diplexer on the secondcommunication path; and applying a third phase shift to the third radiofrequency receive signal between the first diplexer and the second radiofrequency transceiver terminal on the third communication path.
 13. Themethod of claim 12 further comprising: combining the first and secondradio frequency transmit signals at a splitter; and providing thecombined first and second radio frequency transmit signals to theantenna.
 14. The method of claim 13 further comprising: combining thirdand fourth radio frequency transmit signals received from the secondradio frequency transceiver terminal at the splitter; and providing thecombined third and fourth radio frequency transmit signals to theantenna.
 15. The method of claim 12 further comprising: destructivelycancelling the first and second radio frequency transmit signals at asplitter coupled to the second radio frequency transceiver terminal. 16.The method of claim 12 further comprising: destructively cancellingleakage of third and fourth radio frequency transmit signals receivedfrom the second radio frequency transceiver terminal at a first splittercoupled to the first radio frequency transceiver terminal; anddestructively cancelling leakage of the first and second radio frequencytransmit signals at a second splitter coupled to the second radiofrequency transceiver terminal.
 17. A radio frequency system comprising:first and second radio frequency transceivers; a first antenna; and adiplexer circuit includes first and second parallel communication pathsextending between the first radio frequency transceiver and the firstantenna, third and fourth parallel communication paths extending betweenthe second radio frequency transceiver and the first antenna, a firstphase shifter configured to apply a first phase shift to a first radiofrequency transmit signal between the first radio frequency transceiverand a first diplexer on the first communication path, a second phaseshifter configured to apply a second phase shift to a second radiofrequency transmit signal between the first antenna and a seconddiplexer on the second communication path, and a third phase shifterconfigured to apply a third phase shift to the first radio frequencytransmit signal between the first diplexer and the second radiofrequency transceiver on the third communication path.
 18. The system ofclaim 17 wherein the second phase shifter is further configured tocoherently sum the first and second radio frequency transmit signals,and wherein the second phase shifter is further configured to coherentlysum third and fourth radio frequency transmit signals received from thesecond radio frequency transceiver.
 19. The system of claim 17 whereinthe first phase shifter is further configured to destructively cancelleakage of third and fourth radio frequency transmit signals receivedfrom the second radio frequency transceiver, and wherein the third phaseshifter is further configured to destructively cancel leakage of thefirst and second radio frequency transmit signals received from thefirst radio frequency transceiver.
 20. The system of claim 17 whereinthe first phase shifter includes a first hybrid transmit splitter, thesecond phase shifter includes a second hybrid receive splitter, and thethird phase shifter includes a third hybrid antenna splitter.